1. Field of the Invention
The present invention relates to an image capture apparatus including an internal time source such as a real time clock.
2. Description of the Related Art
An image capture apparatus such as a digital camera includes an internal time source such as a real time clock (RTC). The image capture apparatus can generate image capture time information based on time information generated by the internal time source. The image capture time information is stored in a storage medium with image data generated by the image capture apparatus.
In a case where a time difference is observed between time information generated by the internal time source and an actual time, a user can set a time of the internal time source. However, in a case where the user set the time manually, the time difference between the time information generated by the internal time source and the actual time may become larger. For example, in a case where the time difference between the time information generated by the internal time source and the actual time is a millisecond time scale, it is highly possible that the time difference between the time information generated by the internal time source and the actual time becomes larger.
To solve the above-described issue, a method for setting a time of the internal time source using precise time information generated by an external time source is discussed. Japanese Patent Application Laid-Open No. 10-28119 discusses a method in which time information generated by a master device is transmitted to a terminal device and a time of the terminal device is set using the time information. According to the method discussed in Japanese Patent Application Laid-Open No. 10-28119, the master device can calculate a delay time generated in a transmission path between the master device and the terminal device in real time and can add the delay time calculated by the master device to the time information generated by the master device. The resulting time information is transmitted to the terminal device to be set to the terminal device.
However, the method discussed in Japanese Patent Application Laid-Open No. 10-28119 has such an issue that the delay time generated in the transmission path between the master device and the terminal device is taken into consideration but a delay time generated in the terminal device is not considered.
If a user desires to set a high-resolution internal time source more precisely, it is desirable to consider the time delay generated in the terminal device. For example, it is desirable to consider a delay time generated in a communication path between the internal time source (e.g., the RTC) and a time setting unit (e.g., a central processing unit (CPU)) for setting external time information obtained from the external time source to the internal time source. Furthermore, for example, it is desirable to consider a delay time generated in a communication path between a communication unit for receiving the external time information generated by the external time source and the time setting unit (e.g., the CPU) for setting the external time information to the internal time source (e.g., the RTC).
A method for calculating the delay time generated in the terminal device in real time puts a heavy load on the CPU of the terminal device. Particularly, in a case where the terminal device is the image capture apparatus, if a method for calculating the delay time generated within the terminal device in real time is employed for the terminal device, a release timing may be delayed and a user may miss the best shot.